In recent times the percolator has been increasingly replaced by the automatic filter-type coffee maker. Whereas a percolator simply continuously reboils a small portion of a liquid supply to continuously recirculate it through coffee grounds until the desired strength is obtained, the automatic filter-type coffee maker merely feeds the liquid, which is heated to immediately below the boiling temperature, into a holder in which a quantity of the coffee ground is held. Thus the coffee itself is never boiled, giving it a smoother and less bitter taste, and, at the same time, when a filter paper is used in the holder it is possible to grind the coffee beans more finely and thereby use the coffee more economically.
It has been found that such coffee makers, however, do not produce a coffee which is as aromatic and full in taste as possible. This is mainly due to the fact that the brewing time is relatively short, as the entire quantity of liquid is frequently passed in a very short time through the holder containing the grounds. Thus in the standard automatic filter-type coffee maker the grounds normally float at least partially on the body of hot water in the holder.